The invention relates to a method for the operation of a hybrid drive system as well as a hybrid drive system comprising a first drive machine, in particular an internal combustion engine, and a second drive machine, in particular an electric engine, for a motor vehicle. Other types of drive machines are not excluded. For example two electric machines can be provided as the first and second drive machines or along with an internal combustion engine as a first drive machine a hydraulic machine can be provided as the second drive machine.
Motor vehicles with hybrid drive in the most diverse embodiments have in the case of specific driving cycles a more favorable consumption behavior than motor vehicles which are driven exclusively by an internal combustion engine. Thus they are gaining increasing importance on the market.
If an electric machine is used as the second drive machine, said drive machine can be used as the engine and generator. In the engine function, which requires the supply by a battery, a starting of an internal combustion engine or a use as driving engine is possible. In the use as a generator it serves the purpose of charging the battery, wherein the energy can be obtained from the internal combustion engine or from the recuperation of the kinetic energy of the vehicle.
Hybrid drive systems are for example described in WO 2005/073005 A1, DE 100 49 514 A1 and DE 198 18 108 A1.
A hybrid drive for motor vehicles with a engaging and disengaging transmission is known from DE 199 60 621 A1, said transmission containing a first engaging and disengaging sub-transmission, which can be drive-connected optionally to a carbon fueled engine and/or an electric machine, and a second engaging and disengaging sub-transmission, which is drive-connected to the electric machine, said machine being operable as an electromotor or generator. The first sub-transmission comprises a first countershaft and an output shaft and exhibits six gear steps; the second sub-transmission comprises a second countershaft and the same output shaft and exhibits three gear steps.